Dynamic Design Analysis Method

The Dynamic Design Analysis Method (DDAM) is a US Navy-developed analytical procedure for evaluating the design of equipment subject to dynamic loading caused by underwater explosions (UNDEX). The analysis uses a form of shock spectrum analysis that estimates the dynamic response of a component to shock loading caused by the sudden movement of a naval vessel. The analytical process simulates the interaction between the shock-loaded component and its fixed structure, and it is a standard naval engineering procedure for shipboard structural dynamics.

All mission-essential equipment on board military surface ships and submarines must be qualified for underwater shock loads caused by depth charges, naval mines, missiles, and torpedoes. An underwater explosion nearby a ship or submarine can be devastating to the combat readiness of the vessel. Damage may occur in the form of dished hull plating or even more serious holing of the hull. Moreover, some damage may not be obvious and can occur as a result of shock-wave loading of equipment and systems aboard the vessel. Equipment damage may incapacitate a vessel. Much research effort has been expended in the study of underwater shock, especially during the period after World War II where it became obvious that navy vessels could be disabled by a non-contact underwater explosion. Thus a concerted effort was made to try to make shipboard equipment more resistant to shock. This was achieved through laboratory shock testing of equipment prior to its installation aboard vessels. With the advances in computer simulation and modeling capabilities, it is now possible to simulate a vessel's response to an underwater explosion and to identify potential problems or failures without extensive field testing. By using DDAM analytical techniques, money and time are saved.

The DDAM simulates the interaction between the shock-loaded component and its fixed structure as the free motion of a naval vessel in water produces a higher shock spectrum than a heavy structure would when mounted to a terrestrial surface. The DDAM takes interaction into account in relation to the mass of the equipment, its mounting location, and the orientation of the equipment on the vessel.

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